Functional Groups Of Activated Carbon Research Articles

Removal of the pesticide thiamethoxam from sugarcane juice by magnetic nanomodified activated carbon.

The removal of the neonicotinoid and systemic pesticide thiamethoxam (TMX) from water and sugarcane juice by magnetic nanomodified activated carbon (AC-NP) is proposed. This adsorbent was synthesized and characterized by FTIR, XRD, and SEM, and TMX was quantified by high-performance liquid chromatography coupled to a diode array detector (HPLC–DAD). The AC-NP was efficiently synthesized using a co-precipitation method and the impregnation of magnetite (NP) in the activated carbon (AC) was assessed by the crystalline planes found in the AC-NP structure shown in the XRD diffractograms. The AC-NP FTIR analysis also indicated predominant bands of Fe–O stretching of the magnetite at 610–570 cm−1. Functional groups in AC and AC-NP were identified by absorption bands at 3550 and 1603 cm−1, characteristic of O–H and C = C, respectively. The TMX adsorption kinetics in sugarcane juice was the pseudo-second-order type with r2 = 0.9999, indicating a chemical adsorption process. The experimental sorption capacity (SCexp) for both TMX (standard) and TMX-I (insecticide) by AC-NP were 13.44 and 42.44 mg/g, respectively. Seven non-linear isotherm models (Langmuir, Freundlich, Dubinin-Radushkevich, Toth, Hill, Sips, and Redlich-Peterson) were fitted to the experimental adsorption data of TMX and TMX-I by AC-NP. Considering the standard error (SE), Freundlich, Langmuir, and Sips were the most appropriate models to describe the TMX adsorption, and Hill’s best adjusted to TMX-I experimental data. The chromatographic method was highly satisfactory due to its high selectivity and recovery (91–103%). The efficiency of AC-NP in the sorption of TMX was confirmed by the excellent values of SCexp and sorption kinetics.

Enhanced CO2 Adsorption on Activated Carbon‐Modified HKUST‐1 Composites

AbstractMesoporous activated carbon (AC)‐modified HKUST‐1 composites with different AC contents were prepared and were used for CO2 adsorption. The structure and physiochemical properties of the composites were characterized by scanning electron microscopy(SEM), X‐ray diffractometer(XRD), thermogravimetry(TG) and nitrogen adsorption techniques. The results showed that the surface area and micro pore volume for the HKUST‐1@AC composites increase obviously compared to the HKUST‐1. Especially, the HKUST‐1@AC/2% gave the maximum specific surface area of 1145.71 m2/g and micropore volume of 0.4363 mL/g, resulting in highest CO2 adsorption capacity of 155.7 mg/g, which is almost two times than that of the unmodified HKUST‐1. The content of oxygen‐containing functional groups in AC also play an important role in CO2 adsorption for the HKUST‐1@AC/2% composites, and the optimum content of oxygen‐containing functional groups for the coconut shell AC is about 2.9 mg/g. This might be due to that HKUST‐1 grows along the surface of AC with rich oxygen‐containing functional groups, and a large number of micropores are formed between the two interfaces, therefore increasing CO2 adsorption amount.

Preparation of Nickel Nanoparticles Doped with Activated Carbon and Their Hydrogen Uptake at Room Temperature

This study investigates the hydrogen adsorption properties of activated carbon (AC) doped with nickel nanoparticles, and the effects of surface oxygen functional groups in AC on hydrogen uptake at room temperature. The oxidized AC (AC_OX) sample was prepared by mixing AC in a mixture of H2SO4, deionized water and HNO3 solution. By using an electroless plating process, nickel was deposited into oxidized AC (AC_OX) and denoted as Ni/ AC_OX. The oxidized activated carbon was characterized by Fourier transform infrared spectroscopy (FTIR) and Raman spectra to obtain the functional groups and structural information, respectively. After acid oxidation treatment, the integrated intensity ID/IG for the AC_OX sample is higher than that for the AC sample, indicating that the presence of defects on the former is more obvious than that on the latter. The defects facilitate the adsorption of gases and serve as reactive sites for chemical reactions, and thus surface defects are a key to the nucleation, growth, and stability of metal clusters on the support. The particle size distribution and morphology of nickel were also characterized by SEM and TEM. The SEM image of Ni/AC_OX is apparent that the deposited Ni catalyst has a narrow distribution of particle sizes between 10-20 nm in diameter, nickel content of approximately 8~10 wt. %. The specific surface area (SSA) of samples was determined at 77 K with an analyzer Quantachrome Autosorb-1 using N2 as the adsorbent. The BET surface areas of the AC, AC_OX and Ni/AC_OX samples were determined to be 1100, 870 and 340 m2/g, respectively. In addition, the total pore volumes for samples AC, AC_OX and Ni/AC_OX were 0.7, 0.55 and 0.22cc/g. The acidic oxidation treatment has very little impact on the texture of pristine AC. The decrease in SSA and pore volume in the Ni/AC_OX sample was attributed to the filling and blockage of pores of Ni by an electroless plating process. The pore size distribution patterns of AC, AC_OX and Ni/AC_OX are concentrated below 2 nm, with clear peaks at 0.7 and 1.4 nm. Hydrogen uptake measurements of AC, AC_OX and Ni/ AC_OX were performed using a commercial Sievert’s apparatus. The Raman and FTIR spectra demonstrated that the oxidized AC exhibited a slightly defective surface and oxygen functional groups. The hydrogen uptake of AC, AC_OX and Ni/AC_OX is 0.35, 0.21 and 0.58 wt.%, respectively. The RT hydrogen uptake of catalyst-free AC supports is proportional to the specific surface area and micro-pore volume The acidic oxidation treatment of AC sometimes causes a reduced pore volume and specific surface area, resulting in decreased hydrogen adsorption. It has been reported that oxygen functional groups on carbon can help hydrogen adsorption through the increased hydrogen binding energies. We thus speculated that Ni catalysts supported on oxidized AC could compensate for the low specific surface area, and thus achieve a hydrogen uptake comparable with that of pristine AC. Compared to the RT hydrogen uptake for the pristine AC sample of 0.35 wt%, the amount of hydrogen uptake for Ni/AC_OX is enhanced via spillover by a factor of 1.66. The findings further suggest that surface functionalization is essential for effective doping of Ni catalysts onto AC supports for the spillover process. Figure 1

Redox-Active Oxygen-Containing Functional Groups in Activated Carbon Facilitate Microbial Reduction of Ferrihydrite.

Carbonaceous materials are commonly used in agronomic and environmental applications primarily as geosorbents, but their redox properties that may affect biogeochemical reactions are rarely documented. Herein, the role of activated carbon (AC) mediating microbial reduction of ferrihydrite is studied. Our batch experiment results show that AC facilitated the reduction of ferrihydrite by Shewanella oneidensis MR-1, but the pretreatment of AC with HNO3 further increased the rate of reduction. The redox-active oxygen-containing functional groups in AC were found to be responsible for the enhancement of the microbial reduction of ferrihydrite. This conclusion was supported by the electrochemical evidence that showed that the electron exchange capacity (EEC) of AC was facilitated due to the presence of quinone/hydroquinone groups and strongly positively correlated with the content of C═O groups. Moreover, the coprecipitation of vivianite and siderite was found in the products in the presence of AC, but siderite only was present in the absence of AC. The proper identification of potential functional groups in AC-mediating electron transfer during microbial reduction of ferrihydrite provides insights into the mechanism of reaction and potential roles carbonaceous materials may play in biogeochemical redox processes and, consequently, the fate of contaminants in the environment.

Synergistic Effect of Nitric Acid Modified and Cu(II)-Loaded Activated Carbon on Catalytic Ozonation

The surface properties and performance of activated carbon (AC) used for catalytic ozonation were investigated after nitric acid modification (N-AC) and Cu (II)-loaded (N-Cu-AC). The results showed that the nitric acid modification could increase the amount of surface functional groups of AC. As a result, the adsorption capacity and catalytic activity of AC could be improved. The surface functional groups and Cu (II)-loaded of N-Cu-AC showed a synergistic effect on catalytic ozonation, where the catalytic activity of Cu (II)-loaded was more stable. N-Cu-AC was an effective and reusable catalyst for catalytic ozonation. The highest TOC removal efficiency of 58.0% could be achieved when N-Cu-AC was used for 60 min-catalytic ozonation treatment of acid red 3R.

Influence of KOH/Coke Mass Ratio on Properties of Activated Carbons Made by Microwave-Assisted Activation for Electric Double-Layer Capacitors

Activated carbons (ACs) are obtained by microwave-assisted activation of petroleum coke with KOH as an activation agent and used as electrode materials for electric double-layer capacitors. The pore structure and functional groups of ACs are characterized by Fourier transform infrared spectroscopy and thenitrogenadsorptiontechnique.Theresultsshowthatboththespecific surfacearea(SBET)andthetotal pore volume (Vt) of ACs go through a maximum as the KOH/coke mass ratio increases. At 5:1 of the KOH/coke mass ratio, SBET of AC (denoted as AC5/1) made by microwave-assisted activation is 2312 m 2 g -1 , withVtof 1.13 m 3 g -1 , whileSBET of AC made by conventional activation is only 532 m 2 g -1 , with Vt being at 0.24 m 3 g -1 . The microwave-assisted KOH activation process is capable of creating and enlarging micropores of petroleum coke by increasing the KOH/coke ratio from 3:1 to 5:1. Nevertheless, some micropores are destroyed when the KOH/coke ratio is 6:1. The specific capacitance of AC5/1 electroderemainsat246.0Fg -1 evenafter1000charge-dischargecycles.ForthecapacitormadeofAC5/1 or AC3/1 heated at 1073 K, the energy retention ratio after 1000 cycles is 75.1 or 79.6%.